This invention relates to a watertight seal used between two parts having relative motion and more particularly to a seal to be used between moving transducer surfaces to form a water pressure tight joint with minimum acoustic energy loss.
Transducers which are to be utilized in undersea applications are constructed of an assembly of one or more deformable shells arranged in an axially displaced formation with shell end caps at the outermost extremities of the assembly and joint seals between adjacent transducer shells. The joint between the shells of the assembly and the joint at an end cap must be sealed to cause the interior of the shells to be watertight yet allow each shell to expand and contract freely with respect to adjoining shell or the shell end cap. The joint between the shells and end caps must in addition, ideally allow each shell to move freely without mechanical constraint with respect to its adjoining shell or end cap.
Existing methods of fabrication of joint seals, where the ends of the shells are axially aligned with a separation or gap between the adjacent shells, have the gap potted with an elastomer. The axial assembly of shells may alternatively be covered with an elastomer boot thick and stiff enough to withstand the operating depth water pressure. Another method for sealing adjacent shells is to provide a face sealing element, such as a gasket, between the shells and allow the face of one joint to slide on the face sealing element relative to the adjacent shell face. The aforementioned joints resist motion because of the sliding friction between surfaces or because of shear deformation of the interconnecting elastomer, both resulting in large energy losses. In addition, when a joint is potted with an elastomer or when the assembly of shells are covered with a boot, disassembly becomes difficult and usually results in destroying the sealing elastomer.
It is therefore an object of this invention to provide a joint seal which will allow freedom of motion between adjacent surfaces with minimum acoustic energy loss while providing a water pressure-tight seal and allowing disassembly and reassembly without destruction of the seal.